Abstract
Because tissue optics limits the treated volume during anti-tumor Photodynamic Therapy (PDT), its conjugation with prior tissue debulking has been suggested clinically. In this context, the conjugation of radiofrequency ablation and PDT has already been demonstrated. However, the basic principles that enable the success of these protocols have not been discussed. This proof-of-principle study analyzes the possibility of conjugating electrosurgery (ES) and PDT, analyzing different sequences of photosensitizer (PS) administration in an animal model. The animals were distributed over five groups: ES, PS+Light, PS+ES, ES+PS+Light and PS+ES+Light. The PS Photogem was administered systemically. An electrosurgical unit (480 kHz) was used to remove a portion of the liver, leaving a plane surface for PDT illumination (630 nm, 150 J/cm²). Fluorescence was collected during the stages of the experiment to monitor the PS accumulation. After 30 hours, histological processing was performed. The fluorescence spectra revealed strong Photogem emission in both administration sequences (ES+PS; PS+ES), and little PS bleach after ES was observed. The maximum necrosis depth was observed for the PS+ES+Light group—(716 ± 75) μm—higher than its respective control group (160 ± 28) μm, proving successful conjugation. Histological features from ES and PDT on both conjugation sequences were observed. Pre-photosensitized tissue presented decreased ES-related thermal damage. A simple physical hypothesis, based on the Joule effect and the tissue electrical conductivity, was proposed to support these findings. In conclusion, the results successfully demonstrated the possibility of conjugating ES and PDT in a single protocol.
Highlights
Photodynamic Therapy (PDT) is a technique used to attack tumors and localized infections
A decrease in the full width at half maximum (FWHM) is observed on the tissue fluorescence damaged by electrosurgery
Namely the PS+ES+Light, presented a superior total depth of treatment, which would be more recommended in the clinical ablation of lesions
Summary
Photodynamic Therapy (PDT) is a technique used to attack tumors and localized infections. It begins with the administration of a photosensitizer (PS), which concentrates in the tumor after a characteristic accumulation time. Conjugation of Electrosurgery and Photodynamic Therapy chemical and biological processes, leading to tumor death. Most anti-tumor PDT protocols employ Hematoporphyrin Derivates (HpD) as photosensitizers. Photogem has presented promising results to treat different types of tumors since its appearance [3]. It is usually excited by red light (~ 630 nm). PDT alone is not effective in treating bulky tumors
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